<nav class="navbar navbar-default">
  <div class="container-fluid">
    <!-- Brand and toggle get grouped for better mobile display -->
    <div class="navbar-header">
      <button type="button" class="navbar-toggle collapsed" data-toggle="collapse"
              data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
        <span class="sr-only">Toggle navigation</span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
      </button>
      <a class="navbar-brand" routerLink="/" routerLinkActive="active">云加</a>
    </div>

    <!-- Collect the nav links, forms, and other content for toggling -->
    <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
      <ul class="nav navbar-nav">
        <li class="dropdown">
          <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true"
             aria-expanded="false">基础编程<span class="caret"></span></a>
          <ul class="dropdown-menu">
            <li><a href="#">Java</a></li>
            <li><a href="#">JavaScript</a></li>
            <li><a href="#">Python</a></li>
            <li><a href="#">C/C++</a></li>
            <li><a href="#">Swift</a></li>
          </ul>
        </li>
        <li class="dropdown">
          <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true"
             aria-expanded="false">云+<span class="caret"></span></a>
          <ul class="dropdown-menu">
            <li><a href="#">云加Python</a></li>
            <li><a href="#">云加Nodejs</a></li>
            <li><a href="#">云加PHP</a></li>
            <li role="separator" class="divider"></li>
            <li><a href="#">阿里云</a></li>
            <li><a href="#">腾讯云</a></li>
            <li><a href="#">SAE</a></li>
            <li><a href="#">BAE</a></li>
          </ul>
        </li>
        <li class="dropdown">
          <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true"
             aria-expanded="false">学科<span class="caret"></span></a>
          <ul class="dropdown-menu">
            <li><a href="#">Web前端</a></li>
            <li><a href="#">iOS应用开发</a></li>
            <li><a href="#">Android应用开发</a></li>
            <li role="separator" class="divider"></li>
            <li><a href="#">Android系统定制</a></li>
          </ul>
        </li>
        <li><a href="http://plter.com" target="_blank">博客</a></li>
      </ul>
      <ul class="nav navbar-nav navbar-right">
        <li><a routerLinkActive="active" routerLink="/about">关于</a></li>
      </ul>
    </div><!-- /.navbar-collapse -->
  </div><!-- /.container-fluid -->
</nav>
